Method of dyeing acrylic fibers using a cupric salt-phenylphenol reaction product



United States Patent-O1 METHOD OF DYEING ACRYLIC FIBERS USING A CUPRIC SALT PHENYLPHENOL REACTION PRODUCT Cyril G. Evans, Clemson, S. C., assignor to Deering Milliken Research Corporation, Pendleton, S. (1., a corporation of Delaware No Drawing. Application July 29, 1953, Serial No. 371,147

Claims. (Cl. 8-55) The present invention relates to a method of dyeing acrylic fiber.

In recent years there has been developed a new synthetic fiber known as acrylic fiber which name is derived from the fact that the fiber is prepared from polymeric acrylonitrile or copolymers of acrylonitrile and related vinyl compounds. The fiber is currently sold under a variety of trade names including Orlon, Dynel and Acrilan. With the advent of the new fiber it has been necessary to develop new methods of dyeing since it was found very early in the development of the new synthetic fiber that the older conventional methods of dyeing were incapable of giving satisfactory penetration and depth of color.

Probably the most widely used and most successful of the new dyeing methods for acrylic fiber is known as the cuprous ion method. This method consists in adding a cupric salt and a reducing agent to an aqueous bath containing the fiber and an acid dye and maintaining the bath at or very near the boiling point during the dyeing operation. It is known that in this method the copper sulfate and the reducing agent react within the bath to produce copper in the cuprous valence state. It is theorized that the cuprous copper is then absorbed by the acrylic fiber thereby creating an afiinity for acid dyes. Despite the success of this method it has several disadvantages. The greatest disadvantage results from the fact that the addition of the reducing agent to the dye bath is very critical and as a result it has been necessary to devise rather elaborate methods for controlling the addition of the reducing agent. cussed in the American Dyestuff Reporter, vol. II, No. 3, pp. 76 to 80, wherein there is presented a brief review of the cuprous ion method of dyeing. It can be seen from this publication that the cuprous ion method is undesirably complicated and that close control is required in order to obtain satisfactory results.

In view of the difficulties in practicing the cuprous ion method, it is an object of the present invention to provide a method for dyeing acrylic fiber which does not require the complex controls of the former method.

It is a further object of the invention to provide a method for dyeing acrylic fiber which is considerably faster than the previously known cuprous ion method.

It is still another object of the invention to provide a method for dyeing acrylic fiber which does not require the addition of a reducing agent to the dye bath.

The method of the present invention is based on the dis-- covery that an aqueous bath containing an acid dye, a cupric salt and a phenylphenol can be rendered suitable for dyeing acrylic fiber by subjecting the dye bath to a preliminary boiling.

While the presence of a cupric salt in the dye bath is common to both the method of the present invention and the cuprous ion method, it is believed that this is the only similarity between the two methods. There is evidence to show that in the method of this invention the successful results are attributable to the formation of One such control is disice a complex between the cupric salt and the phenylphenol and that reduction of cupric ions to cuprous ions does not occur to any significant extent.

I am aware that paraphenylphenol has been frequently employed in dye baths and other textile treating baths as a swelling agent. I am also aware that paraphenylphenol has been sometimes employed in the capacity of a swelling agent as an ingredient of the dye bath in the cuprous ion method hereinabove described. I However, in my invention the phenylphenol does not appear to function as a swelling agent but instead appears to react chemically with one or more of the other ingredients of the bath and the presence of a phenylphenol in the dye bath is essential to the method of the invention.

The preparation of the dye bath in the present invention can be accomplished merely by boiling a bath containing, in certain proportions to each other, an acid dye, a cupric salt and a phenylphenol. The boiling of the bath appears to efiect a chemical change which, as above stated, is believed to be accompanied by the formation of a complex between the cupric salt and the phenylphenol. It is theorized that in some manner the complex alttaches itself to the acrylic fiber and-thereby creates an affinity for the dye.

It has been found that the length of time which the bath must be boiled in order to render it suitable for the dyeing operation is a function of both the temperature and the concentration of the ingredients in the bath. Accordingly, the time required for boiling may be materially shortened either by raising the boiling point of the bath (through the employment of super-atmospheric pressure) or by increasing the concentration of the ingredients above the concentration normally used in a dyeing operation and, in the latter case, diluting the bath to the final desired concentration after the preliminary boiling. By observance of either or both of these expedients the time can be shortened to about one hour or even less. Without the observance of either expedient, the bath would have to be boiled for several hours and, therefore,-

in the preferred embodiments of this invention the bath is boiled either at superatmospheric pressure or at a concentration greater than that normally used in the final dyeing operation, or both. As a specific illustration of the preceding statement, a dye bath of normal concentration which requires a two hour boiling period at atmospheric pressure can be prepared by boiling only ten minutes under 15 pounds gauge pressure.

Generally speaking, it is preferred in most dyeing operations involving the application of an acid dye to have a. concentration of dye in the bath equal to from about 0.3 to about 2.5 percent by weight of the bath for heavy shades. .When a bath of this concentration which contains also the proportionate amounts of a cupric salt and a phenylphenol is boiled in accordance with this invention preparatory to the actual dyeing operation, an impractically long boiling period is required. However, by boiling a bath. containing the dye in a concentration, for example, equal to 7.5%, the boiling time may be shortened to less than. one hour, the bath subsequently being diluted to the desired concentration for dyeing. This represents the first of the preferred embodiments of the inven tion.

The proportion of ingredients in the bath is fairly critical although the total concentration of ingredients is not although a high concentration is preferred as explained hereinabove. It has been found that the cupric salt should be present in an amount up to about 200%, preferably from about 50 to about 70%, by weight of the dye and the phenylphenol in an amount up to about 200%, preferably from about 30 to about 60%, by weight of the dye. Amounts of cupric salt above the stated range are unsatisfactory because during the sub-- sequent dyeing operation the yarn will acquire a coppery tint and an undesirable stiffness. Amounts of cupric salt below the stated range are not particularly harmful but there will not be obtained during the dyeing operation the desired exhaustion of the dye. It is mentioned at this point that the amount of cupric salt will vary somewhat within the above range depending on the particular dye that is being used and on the particular cupric salt that is being employed. With many dyes the optimum amount of cupric salt to be used is about 65% by Weight of the dye and with other dyes the amount of cupric salt can easily be determined by simple experimentation. Keeping within these proportions, the concentration of ingredients in the bath at the time of the preliminary boiling may be as high as desired as long as the bath remains a liquid.

In thev second preferred embodiment of the invention, the bath containing the ingredients in the specified proportions is subjected to boiling at a super-atmospheric pressure of at least about five pounds per square inch gauge. The slight increase in the boiling point which is thereby obtained surprisingly lowers the time required for boiling the bath usually to about minutes or less. There is no fixed upper limit on the degree of superatmospheric pressure except that imposed by the decomposition temperature of the ingredients and an increase in the pressure above five pounds per square inch will further decrease the time required for the preliminary boiling of the bath. Still further decreases in the time required for boiling the bath can be effected by the employment of both superatmospheric pressure and a dye bath of increased concentration.

It has been found that the preliminary boiling is accompanied by a lowering of the pH of the dye bath. For example, in a dye bath containing Roracyl Dark Green B (Du Pout). copper sulfate and paraphenylphenol, the pH is lowered from about an initial 3.5 to about 2.6 at which point the preparation of the dye bath is complete. The pH measurement, therefore, affords a convenient method for determining the moment when the dye bath is properly prepared for the dyeing operation. However, the pH varies according to the ingredients of the bath and the pH figures stated above are applicable only to the combination of Roracyl Dark Green B, copper sulfate and paraphenylphenol. The actual pH change for each different dye bath can best be determined by the experimental dyeing of yarn samples after varying periods of boiling. In this manner, a pH change for each dye bath can be established and there is thus provided a simple and convenient method of control which can be employed in all subsequent processing with a bath of the same composition.

In the practice of the invention, almost any cupric salt that is water-soluble is a satisfactory ingredient of the dyebath. However, by far the best results from the standpoints of shade and penetration can be obtained using copper sulfate and consequently, this compound is the preferred cupric salt. Satisfactory dyeing can also be obtained, however, by the use of such cupric salts as copper nitrate, copper acetate and cupric chloride.

The phenylphenol employed as an ingredient of the dye bath in the present invention may be either ortho-, metaor para phenylphenol. Of these compounds, paraphenyl phenol is preferred because by far the best results are obtainable therewith. Orthoand metaphenylphenol are operative but they exhibit a tendency to steam distill and evaporate from the dye bath which in consequence loses its potency before the dye is exhausted.

The dye baths prepared in accordance with the present invention are capable of producing highly satisfactory dyeings on any type of fiber, i. e., both staple and continuous filament fiber, which is prepared from various polymers and copolymers of acrylonitrile. The oomercially available and which are characterized by their application from an acidic dye bath. Such dyes include, for example, Anthraquinone Blue SKY (C. I. 1088), Anthraquinone Green GN (C. I. 1078), Orange II (C. I. 151), Quinoline Yellow PN (C. I. 802), Anthraquinone Blue RA (Du Pont), Anthracene Blue WR (1,2,4,5,6,8- hexahydroxyanthraquinone), as well as many other dyes. Suitable acid and direct dyes are also sold under various trade names such as Roracyl Orange R (Du Pont), Roracyl Dark Green B (Du Pont), Pontacyl Fast Red AS (C. I. 176), Pontacyl Rubine R (C. I. 179), Roracyl Violet 2R (Du Pont), Cuprofix Yellow G Conc. (C. I. 260), and Cuprofix Violet 2BL (Pr. 429).

After the dye bath has been boiled for a time in accordance with the considerations mentioned above and then diluted, if necessary, the bath is ready for the actual dyeing operation. .In this operation no unusual precautions are necessary and satisfactory dyeings can be obtained quite rapidly by merely immersing the yarn or fabric to be dyed in the boiling dye bath and sufiicient yarn can be dyed in this manner to substantially exhaust the bath. Any of the customary and conventional pieces of apparatus that are presently employed in the dyeing of staple yarn or fabric can be employed. The length of time for the immersion of the yarn or fabric is subject to many variations and will vary according to the temperature of the dye bath, and the depth of shade desired.

In dyeing a filament fabric, it is preferable to employ an enclosed dye jig as is illustrated in some of the later examples. In an apparatus of this type, the fabric is wound on a pair of reels suspended above the dye bath and the fabric between the reels is immersed in the dye bath by means of submerged rollers. The fabric is then continuously drawn through the bath from reel to reel, the reels automatically reversing direction when the fabric on the feed reel becomes substantially unwound. In the operation of the jig, the dyeing can be accelerated by not only maintaining the temperature of the bath at the boiling point but also by maintaining the temperature of the wet fabric on the reels as near the boiling point as possible. The latter can be conveniently accomplished in an enclosed jig by providing perforated steam pipes adjacent to the reels. In maintaining the bath at the boiling point, the introduction of live steam into the liquor should be avoided since this appears to decompose the bath and results in poorer dyeings.

In order to illustrate the invention and its attendant advantages, the following examples are given.

Example I A dye bath was made up by dissolving the following ingredients in 600 m1. of water:

The resultant solution was then placed in an ordinary household pressure cooker and it was boiled therein under a pressure of 15 p. s. i. g. for a period of about 20 minutes. During the boiling of the bath, the pH was lowered from about 3.4 to about 2.6.

A piece of continuous filament Orlon fabric which had been previously scoured was then immersed in the dye bath while maintaining the temperature of the dye bath at its atmospheric boiling point, i. e., approximately 213 F. After an immersion time of about 15 minutes, the fabric had acquired an excellent black color. The penetration of the dye was also excellent after 1 hour immersion and the color was fast to repeated washings and quite exceptionally fast to light (over 400 hrs.).

Example 2 A dye bath was made up as in Example 1 except that the amounts of dye, copper sulfate and purasist RA were tripled, thus providing a bath having a concentration three times that of the bath of Example 1.

The bath was then heated to its boiling point (approximately 213 F.) audit was allowed to boil for 10 minutes during which time the pH of the bath was lowered from 3.1 to 2.4. Thereafter the bath was diluted to the concentration of the bath employed in Example 1 by the addition of water. The bath was again heated to its boiling point and a piece of continuous filament Orlon fabric was immersed in the bath while maintaining the temperature of the bath at the boiling point. After an immersion time of approximately 15 minutes, the fabric was dyed a good black color that was fast to washing and the penetration of the dye was excellent after 1 hour.

Example 3 In order to demonstrate the fact that the function of the phenylphenol in the dye bath is not that of a swelling agent in the present invention, the following experiment was performed.

A dye bath was of Example 1 exactly except that the omitted from the bath.

A piece of continuous filament Orlon fabric which had been previously scoured was treated by immersion in a concentrated aqueous solution of paraphenylphenol until a maximum swelling of the fibers was observed. Thereafter the fabric was immersed in the previously prepared dye bath While maintaining the dye bath at its atmospherlc boiling point. The resultant dyeing was extremely poor, the fabric being dyed only a moderate gray and the penetration of the dye being noticeably poor.

Example 4 A dye bath was made up as in Example 1. The dye bath was then placed in an open vessel and heated to the boiling point and the boiling was continued, allowing water to evaporate in order to obtain the accelerating effect of an increase in concentration of the ingredients. After 120 minutes the bath had evaporated to one-fifth of its original value. The pH of the bath during boiling was lowered from about 3.4 to about 2.6.

A piece of continuous filament Orlon fabric which had been previously scoured was then immersed in the dye bath while maintaining the temperature of the dye bath at its atmospheric boiling point. After an immersion time of about 45 minutes, an excellent dyeing was obtained.

prepared according to the procedure phenylphenol was Example 5 A dye bath was made up by dissolving the following ingredients in 125 gallons of water:

Copper sulfate The initial dye bath had a pH of 3.4. The entire dye bath was placed in a pressure reaction vessel and was boiled in the vessel under a superatmospheric pressure of 15 pounds p. s. i. g. for 20 minutes. The bath was there after transferred to a dye jig and heated to its boiling point. Two hundred twenty five pounds (225 lbs.) of continuous filament Orlon fabric which had been previously scoured was then dyed in the jig, taking precautions to keep the temperature of the dye bath at the boiling point, and to maintain the temperature of the fabric on the reels of the jig as close to the boiling point as possible. After the jig had been in operation for about 3 hours, the cloth had been dyed a deep black color and was removed. Subsequent examination of the cloth revealed that the dyeing was excellent and tests showed the dyeing to be fast to repeated washings and exceptionally fast to light (in excess of 400 hrs.).

Example 6 The procedure of Example 1 was followed with the exception that copper nitrate was substituted for copper sulfate. The cloth was dyed a good black color but the speed of dyeing was much slower than in Example 1.

Example 8 The procedure of Example 1 was followed substituting copper acetate for the copper sulfate of Example 1.

' Again a good dyeing was obtained although within a 2 hour period the cloth became only dark green in color.

The foregoing examples demonstrate the simplicity of the method of the present invention and its many advantages. It is to be noted particularly that no extensive controls are necessary during the dyeing operation and that the dyeings which are obtained are excellent. As has been demonstrated, one of the advantageous features of the method is that it is not necessary to employ a reducing agent as an ingredient of the dye bath. The exhaustion of the dye is also excellent.

It is intended to cover all changes and modifications in the examples of the invention herein given for the purposes of disclosure, which do not constitute departure from the spirit and scope of the appended claims.

I claim:

1. A method for dyeing acrylic fi-ber which comprises boiling an aqueous dye bath containing a dye selected from the group consisting of acid and direct dyes, an amount of a water-soluble cupric salt up to about 200% by weight of the dye, said cupric salt being one that ionizes in aqueous solution to furnish cupric ions, and an amount of a phenylphenol up to about 200% by weight of the dye, and thereafter entering acrylic fiber in the dye bath and dyeing the same therein while retaining the copper substantially entirely in the cupric valence state.

2. A method for dyeing acrylic fiber which comprises boiling under a superatmospheric pressure an aqueous dye bath containing a dye selected from the group consisting of acid and direct dyes, an amount of a water-soluble cupric salt up to about 200% by weight of the dye, said cupric salt being one which ionizes in aqueous solution to furnish cupric ions, and an amount of a phenylphenol up to about 200% by weight of the dye, and thereafter entering acrylic fiber in the dye bath and dyeing the same therein while retaining the copper substantially entirely in the cupric valence state.

3. A method according to claim 1 in which the concentration of dye in the bath at the time of boiling is greater than that desired for the dyeing operation and in which 7 the bath is diluted subsequent to the boiling and Prior to the dyeing operation. 7

4. A method according to claim 2 in which the copper salt is coppe sulfate.

5. A method according to claim 2 in which the phenylphe-nol is paraphenylphenol.

6. A method according to claim 2 in which the cupric salt is copper sulfate and the phenylphenol is paraphcnylphenol.

7. A method according to claim 3 in which the copper salt is copper sulfate,

8. A method according to claim 3 in which the phenylphenel is paraphe y ph nol- A method according to aim 3 i hi h th upric salt is copper sulfate and the phenylphenol is paraphenyl- 1 phenol.

10. A method according to claim 2 in which the dye is an acid dye.

References Cited in the file of this patent FOREIGN PATENTS Belgium July 31, 1951 OTHER REFERENCES General Dyestuflf Corp, Dyeing Synthetic Fibers, pages 0 s and 9, Nov. 23, 1951.

y to 21, March 1953. i) 

1. A METHOD FOR DYEING ACRYLIC FIBER WHICH COMPRISES BOILING AN AQUEOUS DYE BATH CONTAINING A DYE SELECTED FROM THE GROUP CONSISTING OF ACID AND DIRECT DYES, AN AMOUNT OF A WATER-SOLUBLE CUPRIC SALT UP TO ABOUT 200% BY WEIGHT OF THE DYE, SAID CUPRIC SALT BEING ONE THAT IONIZES IN AQUEOUS SOLUTION TO FURNISH CUPRIC IONS, AND AN AMOUNT OF A PHENYLPHENOL UP TO ABOUT 200% BY WEIGHT OF THE DYE, AND THEREAFTER ENTERING ACRYLIC FIBER IN THE DYE BATH AND DYEING THE SAME THEREIN WHILE RETAINING THE COPPER SUBSTANTIALLY ENTIRELY IN THE CUPRIC VALENCE STATE. 